I think it's good to modify if it in some way make you like the vehicle better. I really want to put bigger rims on the IQ for looks, but I'll probably go smaller to keep the mileage and give it a better ride. I will only modify within reason... so it wouldn't make sense to me if I put a $5k paint job on a $15k car.... the same with wheels and other things that can't be removed from the vehicle.
For anyone that's worried about losing their warranty. As long as the part you installed doesn't have anything to do with what ever part would need warranty repair or replacement the dealership is legally binded to honor your warranty. So for example you install a new exhaust and there's a problem with the ignition system, they're still supposed to cover the warranty. Even if its actually related to the problem they still have to prove that the part you installed is related to what caused the problem.
Apparently the iQ is not unique enough for me (geez!). I bought practically the whole catalog of dealer parts, but that's still not unique enough (same parts y'all have, right?). I'm having a lot of fun dreaming up further things to do to it...and then actually doing some.
I'm allergic to sponsorship, I'll probably even remove the Scion and iQ tags (I'm developing a leopard theme, probably slap on a Thundercats logo just for fun). And I love pride of having done something cool with my own hands. It will probably be a high-end import show car when I tire of it. Art is never really finished, only abandoned.